As there is still neither proper treatment nor reliable prophylaxis, animal models will remain important in the study of HO. Currently, there are 6 different animal models regularly used for the study of acquired HO. Some of these models can reflect a merely particular part of the disease. Hence, selection of the appropriate animal model for the study of HO is exceedingly important. The present paper reviews the history and major features of the different animal models of acquired HO, and reveals some of the insights gained through the study of animal models; important biochemical and pathophysiological key features are highlighted. Clinical studies have proved indometacine, celecoxib and radiation therapy to be effective in reducing the occurrence of HO, but not always be able to prevent it.